Frequency control apparatus



July 31, 1934. L. A. GEBHARD FREQUENCY CONTROL APPARATUS Filed Dec. 14, 1931 2 Sheets-Sheet l IN VEN TOR. W

TORNEY BY/fl/flAT July 31; 1934. 1.. A. GEBHARD FREQUENCY CONTROL APPARATUS Filed Dec. 14, 1931 2 Sheets-Sheet 2 ll IIIIIIII! I!!! .IIII'IIIIIIIIIIIII INVENTOR. 04410 61 BY A TTORNEY Patented July 31, 1934 UNETED STATES PATENT OFFICE 9 Claims.

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) My invention relates broadly to frequency control apparatus and more particularly to a constant temperature cabinet structure for a frequency control apparatus.

One of the objects of my invention is to provide a constant temperature controlled cabinet structure for frequency control apparatus in which a continuous circulation of air may be maintained within the temperature controlled cabinet structure for insuring a uniform temperature throughout all parts of the cabinet structure for obtaining precision operation of the frequency control elements within the cabinet structure.

Another object of my invention is to provide a mounting for an electromechanical vibrator within a cabinet structure having means for insuring a continuous circulation of air adjacent the electromechanical vibrator within the cabinet structure for subjecting the electromechanical vibrator to a condition of constant temperature.

Still another object of my invention is to provide an arrangement of frequency control apparatus in which a plurality of electromechanical vibrators are subjected to a uniform temperature within a cabinet structure by the continuous circulation of air currents in the immediate vicinity of the electromechanical vibrators for insuring precision operation of the electromechanical vibrators.

Other and further objects of my invention reside in the method of mounting electromechanical vibrators for operation at constant temperature for accurate maintenance of selected frequencies in an associated oscillator circuit as will be more fully pointed out in the specification hereinatfer following by reference to the accompanying drawings, in which:

Figure 1 is a horizontal sectional view taken through a portion of the constant frequency control cabinet structure of my invention and illustrating certain of the parts in plan View; Fig. 2 is a vertical sectional view through the constant frequency control apparatus of my invention; Fig. 3 is a vertical sectional view through the constant frequency control apparatus taken on line 3--3 of Fig. 2; Fig. 4 is an enlarged cross-sectional view through the central portion of the frequency control apparatus on line 4-4 of Fig. 1, showing the mounting of the thermostat with respect to the frequency control apparatus; and Fig. 5 is a cross-sectional view taken through the mounting plates for the frequency control apparatus on line 55 of Fig. 1.

In order to insure precision operation of electro-mechanical vibrators, it is necessary that the temperature of the electromechanical vibratorsv be maintained substantially constant. The variation in temperature which is permissible must be kept within a very small range. :I have. found that in the construction of transmitters capable of operation on different frequencies over a relatively wide range of frequencies, that temperature gradients within the cabinet structure which houses the electromechanical vibrators often introduces errors which are so magnified in the transmitter circuits as to adversely affect the maintenance of the signaling frequencies. The structure of my invention provides means for reducing temperaturegradients within the cabinet structure which houses the electromechanical vibrators so that variation in temperature is reduced to a minimum and stability of the control improved. The apparatus of my invention includes a plurality of massive plate members each having good heat conductivity. These plate members are supported in horizontal arrange: ment in the nature of shelves by means of a plurality of vertically extending tubular memhere. One of these tubular members provides a housing for a thermostat. The other tubular members are directly connected with the heat conductive shelves and provide a path for air currents through the shelves. The circulation of air through each of the shelves which support the electromechanical vibrators insures substantially uniform temperature for all of the electromechanical vibrators. The passage of air through the several tubes at constant temperature insures an extremely low temperature gradient between the several electromechanical vibrators, thereby insuring accuracy in frequency control. Heating means are provided within'the cabinet structure and a fan so disposed in relation to the heating means as to circulate the air through the tubes and around the electromechanical vibrators for insuring constant temperature throughout the frequency control apparatus and thereby insuring constant frequency control.

Throughout the drawings I have illustrated containers for electromechanical vibrators of the piezo electric crystal type but it will be understood that other forms of electromechanical vibrators may be employed and the temperature of the electromechanical vibrators controlled in a manner similar to the arrangement disclosed herein.

Referring to the drawings in detail, reference character 1 designates the casing which houses the constant temperature control cabinet. Alining of heat resisting materialis indicated generally at 2. The cabinet structure formed by the lining 2 is provided with an internal heater 3, comprising a plurality of looped. heater coils disposed in spaced relation within the cabinet struc ture. A fan 6 is disposed below the turns of heater coil 3 and is driven by motor 4 mounted in bracket 5 on the exterior of the casing. The interior of the cabinet structure is provided with a pair of rails shown at 7 forming guides for the removable frame structure 8 which supports the electromechanical vibrators for the frequency control apparatus. The removable frame structure 8 extends from a vertical panel 9 which is insertable or removable through the front of the cabinet 1 by opening the hinged door 20. A switch 27 is controlled from the front of the apparatus for actuating contact mechanism supported from panel 9 for selecting the particular electromechanical vibrator which is required for sustaining high frequency oscillations in the signaling circuit. The electromechanical vibrators are mounted on horizontally extending shelves 10. The horizontally extending shelves 10 are constructed of metal plates of large heat conductivity. These metal plates are supported in horizontal spaced relation by means of a central vertically extending tube 21 and a plurality of vertically extending tubes 22 disposed symmetrically about the central tubes 21. Tubes 21 and 22 are formed of metallic material having high heat conductivity. The tubes 21 and 22 are directly united to the laterally extending metallic shelves 10 and serve to centrally support the metallic shelves 10 at the same time forming heat conduction paths between the several tubes and the several shelves. The shelves are further centrally braced and supported by means of the channel shaped heat distribution plate 11 at one side and the insulated panel 16 on the other side. The heat distribution plate 11 is connected to the horizontally extending shelves 10 by means of screws 11a. The channel shaped heat distribution plate 11 provides means for supporting the contact clips 12 extending in opposite directions.

1 from each side thereof and secured thereto as indicated at 12a.

The insulated plate 16 is secured to horizontally extending shelves 10 by means of screwsv 16a. The panel 16 provides means for supporting the clips 17 which are secured thereto as indicated at 17a as shown. The clips 12 and 17 engage the oppositely extending terminals on each of the casings 14 and of the electromechanical vibrators. The casings 14 and 15, in the form of the invention illustrated, each contain piezo electric crystal elements although other forms of electromechanical vibrators may be employed. Each of the casings have a base which directly rests upon the heat conductive metallic shelf 10. In this manner the casing for the electromechanical vibrator is established at the same temperature which ex-' ists at the shelf 10. Inasmuch as the tubes 21 and 22 form chimneys through which the heated air is positively driven it will be apparent that an extremely uniform temperature division is insured throughout the several electromechanical vibrators mounted upon the shelves 10. The central tube 21 encloses a thermostat which I have illustrated generally at 23. The thermostat 23 has its lower end supported in the resilient wire basket 24 secured to lower shelf 10 by means ofscrew 25. The upper end of thermostat 23 is secured by'contact clips 26 adjacent the top of the tube 21 from which leads extend to the relay circuit which cuts on andoff the supply-of energy to heater coils 3 in accordance with required temperature conditions. I have illustrated by means of arrows the circulating path for air currents through the frequency control apparatus. It will be observed that the air currents pass vertically through the tubes 21 and 22 and return around the sides of the electromechanical vibrator casings and downwardly through the heater coils 3 for repeated cycles.

I have found the apparatus of my invention extremely practical in its construction and efficient in its operation and While I have described one of the preferred embodiments of my invention I desire that it be understood that modifications may be made and that no limitations upon my invention are intended other than are imposed by the scope of the appended claims.

The herein described invention may be manufactured and used by or for the Government of the United States for governmental purposes without the payment of any royalties thereon or therefor.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. Frequency control apparatus comprising a constant temperature controlled cabinet structure, a frame structure disposed within-said cabinet structure, said frame structure including a plurality of horizontally extending heat conductive superimposed shelf members each adapted to receive an electromechanical vibrator, supporting means for said shelf members, said supporting means comprising a plurality of vertically extending heat conducting tubular members passing through said shelf members and conductively connected with said horizontally extending shelf members for establishing a thermal transfer therebetween, means for circulating air through said vertically extendingtubular members and a thermostat disposed in one of said tubular members.

2. Frequency control apparatus comprising a temperature controlled cabinet structure, a plurality of horizontally extending heat conductive shelf members each adapted to receive an electromechanical vibrator casing, heat conductive tubes thermally interconnecting the central portions of said shelf members and extending therethrough, and means for circulating air through said tubes, a thermostat disposed in one of said tubular members, and an insulated panel and a metallic panel connected to opposite edges of said shelf members in vertical relation thereto.

3. In a frequency control system, a temperature controlled cabinet structure, a frame within said cabinet structure, a heat conductive plate member extending horizontally across said frame, a central tubular member extending vertically from said heat conductive plate member, a plurality of heat conductive plate members carried by said central tubular member in parallel spaced-relation, each of said plate members providing a support for a' casing containing an electromechanically vibratile element, and a thermostat disposed in said central tubular member for controlling the temperature within said cabinet structure,

4. In a frequency control apparatus, a constant temperaturecontrolled cabinet structure, a frame 'within said cabinet structure comprising a plurality of superimposed horizontally extending heat conductive shelves, a central insulated panel connected to one edge of each of said shelves, a central metallic panel connected to the opposite edge of each of said shelves and extending vertically with respect thereto, said shelves each being adapted to receive and support electromechanical vibrator casings thereon, groups of contact elements for said electromechanical vibrator casings carried by each of said panels, a plurality of air circulating tubes extending through said shelves and thermally connected therewith, said tubes including a central member and a multiplicity of symmetrically arranged adjacent members, and means for establishing a forced circulation of air through said tubes and interiorly of said cabinet structure.

5. Frequency control apparatus comprising a constant temperature controlled cabinet structure, a frame within said cabinet structure including a multiplicity of superimposed heat conductive horizontally extending shelves, a vertically extending insulated panel connected to one edge of each of said shelves, a vertically extending metallic panel connected to the other edge of each of said shelves, a plurality of laterally extending contact members carried by said insulated panel and by said metallic panel in positions parallel with the edges of said shelves, a multiplicity of electromechanical vibrator casings each having a pair of terminals thereon adapted to be engaged by said laterally extending contact clips, and a plurality of air circulating tubes thermally connected with each of said shelves and extending vertically through said heat conductive horizontally extending shelves.

6. Frequency control apparatus comprising a constant temperature controlled cabinet structure, a. frame within said cabinet structure, a

horizontally extending heat conductive shelf carried by said frame, a central heat conductive tube extending vertically from said shelf, a plurality of horizontally extending heat conductive shelves extending in parallel relation to said first mentioned shelf and supported by said central tubular member in a relation for establishing a heat exchange path therebetween, said shelves each being adapted to support an electromechanical vibrator casing thereon, a plurality of groups of tubular members extending through said shelves adjacent said central tubular member for establishing paths for the circulation of air therethrough, a thermostat disposed in said central tubular member, and means for creating a forced circulation of air through all of said tubular members.

7. Frequency control apparatus comprising a frame structure, a unit carried by said frame structure, said unit comprising a plurality of horizontally extending shelves and a multiplicity of tubular members extending centrally through said shelves normal to the planes thereof, said shelves being arranged to receive and support frequency control elements thereon said tubular members including a relatively large central member and groups of relatively smaller adjacent members, all of said members establishing heat exchange paths between said shelves and a thermostat disposed in said central tubular member.

8. Frequency control apparatus comprising a plurality of frequency control devices, and means for supporting said devices one above another comprising a plurality of shelves, tubular members extending centrally through said shelves normal to the planes thereof for maintaining said shelves in predetermined spacial relation and providing paths for the circulation of a cooling medium therethrough said tubular members being formed from heat conducting material for transferring heat from one of said means to another and a thermostat disposed in one of said tubular members.

9. In a frequency control unit, a plurality of heat conducting horizontally extending shelves, 

